The heart is a muscular pump with four chambers – two atria which receive blood and two ventricles which pump out blood. The right side of the heart (right atrium and right ventricle) deals with deoxygenated blood (low in oxygen) while the left side (left atrium and left ventricle) handles oxygenated blood (rich in oxygen). There are four valves in the heart which play the vital role of preventing backward flow of blood through the heart and great blood vessels. This essentially ensures that the blood flows in one direction only. Deoxygenated blood enters the right atrium and passes into the right ventricle. It is then pumped out to the lungs where it is oxygenated. The oxygen rich blood then enters the left atrium of the heart and is passed to the left ventricle. From the left ventricle it is pushed out to the rest of the body.

Types of Heart Valves

The heart valves that lie between the atria and ventricles are known as the atrioventricular (AV) valves. These valves are also known as cuspid valves because it has flaps or cusps that close together to form a seal when the ventricles are pumping. This prevents blood in the ventricle from flowing in the wrong direction, which is into the atria. The valves at the junction of the ventricles and great arteries are known as the semilunar valves due to the shape of the leaflets. It prevents blood that leaves the ventricle and enters the respective artery from flowing backwards when the ventricle relaxes.

What are the names of the four heart valves?

The heart valves are as follows :

• Atrioventricular Valves
  • Tricuspid valve lies between the right atrium and right ventricle. It has three flaps.
  • Bicuspid valve or mitral valve lies between the left atrium and left ventricle. It has two flaps.
• Semilunar Valves
  • Pulmonary valve or pulmonic valve lies between the right ventricle and pulmonary artery.
  • Aortic valve lies between the left ventricle and aorta.

How do the heart valves work?

All the heart valves work in the same way, which is to close when the blood is about to flow backwards. However, the process is a little more complex than this.

Atrioventricular Valves

The atrioventricular (AV) valves are made up of flaps that are attached via tendons known as chordae tendinae to small papillary muscles on the heart wall. It allows blood to pass from the atria into the ventricles. When the ventricle contracts the blood pushes the flaps of the AV valve together. However, the force of ventricular contraction may cause the valve to bend backwards but the papillary muscles contract thereby pulling on the chorda tendinae. This holds the flaps of the AV valves firm against the force of the blood pushing on it.

Semilunar Valves

The semilunar valves are like small cups that are flat against the vessel wall when blood is flowing in the right direction. This is during ventricular contraction when blood is expelled out of the heart and through the respective artery (pulmonary artery from the right ventricle, aorta from the left ventricle). However, at the end of ventricular contraction, the blood in the arteries begin to flow backward into the ventricle. This immediately fills the small cups of the respective semilunar valve which enlarges and closes. In this way, blood cannot enter the ventricle from the artery.